Diabetic macular oedema—need for a unified consensus classification based on clinical and imaging features

Diabetic macular oedema (DMO) remains a complex and poorly standardised condition in clinical practice, with various classification systems relying on different diagnostic modalities, including colour fundus photography, clinical biomicroscopy, fundus fluorescein angiography, and optical coherence tomography (OCT). This lack of uniformity complicates diagnosis, treatment decisions, and patient selection for clinical trials. In this interpretive review, we analyse the existing DMO classification systems and propose the C-METRICAL system, which integrates clinical evaluation, OCT imaging, and angiographic findings. The system consolidates the established classifications, like clinically significant macular oedema and the International Clinical DME classification. It incorporates both qualitative and quantitative measures, including OCT metrics, morphological subtypes, relevant biomarkers, and angiographic features such as focal or diffuse oedema and the status of the foveal avascular zone. The C-METRICAL system further accounts for diabetic retinopathy severity and systemic comorbidities, including hypertension and nephropathy, which influence treatment choices and prognosis. Adopting the unified C-METRICAL classification could enhance both clinical trials and practice by addressing all variables influencing DMO at baseline and during follow-up. Future studies are required to demonstrate its clinical utility and effectiveness compared to standalone classification methods.